package main

import (
	"fmt"
	"sync"
)
var m sync.Mutex
var set = make(map[int]bool, 0)

func printOnce(num int) {
	m.Lock()
	defer m.Unlock()
	if _, exist := set[num]; !exist {
		fmt.Println(num)
	}
	set[num] = true
}

func main() {
	slice2 := make([]int, 10)
	slice2 = append(slice2, 2, 3,4,5)
	fmt.Println(slice2)

	// time.Sleep(time.Second)
}
